Generally, in building facility of a company or others, a building facility device managing system for integrally controlling a plurality of building facility monitoring devices for a plurality of air conditioners, lighting devices, door opening/closing devices, and others is installed via a network. Each building facility monitoring device and the building facility device managing system are connected to each other via the Ethernet (Registered trademark) whose communication is generalized with using a communication protocol such as “BACnet” (Building Automation and Control Networking protocol: communication protocol standard for intelligent building network) and “Lontalk” (Local Operation Network: communication protocol standard for connecting a device such as a lighting device, a switch, and a temperature sensor mounted with a neuron chip for operation). On the other hand, in building facility of a company or others, a computer network has been structured along with development of a computer technology so that a lot of personal computers and IP monitoring cameras are connected to a server via an IP network such as LAN based on TCP/IP protocols. However, specifications of the BACnet and the Lontalk which are communication standards on the above-described building facility device managing system side are different from those of the TCP/IP protocols which are communication standard on the IP network device managing system side.
Note that Japanese Patent Application Laid-Open Publication No. 3366228 is cited as a document describing a technique of performing network connection based on a different protocol. This document describes a technique by which the SNMP protocol and the non-SNMP protocol are accessible from each other so that all devices in the network can be monitored and controlled by one monitoring control device, by providing: means for identifying that a signal of a SNMP protocol received from a transmission-source device connected to a network is to be converted into which non-SNMP protocol; means for converting the signal into the non-SNMP protocol used by a transmission-destination device connected to another network with reference to a conversion table prepared by the identifying means, and then, transmitting it to the transmission-destination device; means for identifying that a signal of the non-SNMP protocol received from the transmission-source device connected to the network is to be converted into what type of the non-SNMP protocol; and means for converting the signal into the SNMP protocol used by the transmission-destination device connected to the network with reference to the conversion table provided by the identifying means, and then, transmitting it to the transmission-destination device.